900
FXUS07 KWBC 311901
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MON JUL 31 2023
30-DAY OUTLOOK DISCUSSION FOR AUGUST 2023
THE MONTHLY OUTLOOK FOR TEMPERATURE AND PRECIPITATION FOR AUGUST IS UPDATED
USING THE LATEST TEMPERATURE AND PRECIPITATION OUTLOOKS FOR THE FIRST WEEK OF
AUGUST FROM THE WEATHER PREDICTION CENTER (WPC), THE CLIMATE PREDICTION CENTER
(CPC) EXTENDED RANGE FORECASTS FOR THE 6-10 DAY AND WEEK-2 PERIODS, THE CPC
WEEK 3-4 OUTLOOK, AS WELL AS DYNAMICAL MODEL FORECASTS FROM THE CFSV2 AND GEFS
FOR THE FULL MONTH OF AUGUST. EL NIñO CONDITIONS ARE PRESENT IN OBSERVATIONS OF
THE EQUATORIAL PACIFIC ATMOSPHERIC AND OCEAN, AND ARE LIKELY TO CONTINUE
THROUGH THE MONTH OF AUGUST AND INTO LATER SEASONS. THERE IS A WEAK MADDEN
JULIAN OSCILLATION (MJO) AS INDICATED BY THE VELOCITY POTENTIAL FIELD. HOWEVER,
THE REAL-TIME MULTIVARIATE MJO (RMM) INDEX IS LOW IN AMPLITUDE AND MODEL
FORECASTS SHOW ONLY WEAK PROPAGATION OF THE SIGNAL ACROSS THE WESTERN
HEMISPHERE. MJO IS UNLIKELY TO IMPACT THE CLIMATE OF NORTH AMERICA FOR THE
MONTH OF AUGUST.
THE UPDATED AUGUST TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES ACROSS
ALASKA WITH MORE LIKELY ABOVE NORMAL TEMPERATURES FOR SOUTHEASTERN ALASKA,
SUPPORTED BY DYNAMICAL MODEL FORECASTS FROM THE CFSV2 AS WELL AS CPC OUTLOOKS
THAT FAVOR ABOVE NORMAL TEMPERATURES FOR THE 6-10 DAY, WEEK-2, AND WEEK 3-4
PERIODS. ABOVE NORMAL TEMPERATURES CONTINUE TO BE FAVORED FOR MUCH OF THE WEST,
AS IN THE PRIOR OUTLOOK. HOWEVER, PROBABILITIES OF ABOVE NORMAL HAVE DECREASED
SUBSTANTIALLY ACROSS THE GREAT BASIN, AND THERE ARE NOW EQUAL CHANCES (EC) OF
ABOVE, NEAR OR BELOW NORMAL TEMPERATURES FOR MUCH OF CALIFORNIA, SUPPORTED BY
DYNAMICAL MODEL FORECASTS FROM THE CFSV2, AS WELL AS THE CPC WEEK-2 AND WEEK
3-4 OUTLOOKS. BELOW NORMAL TEMPERATURES ARE FAVORED FOR A SMALL AREA OF THE
NORTHERN HIGH PLAINS, SUPPORTED BY THE LATEST GUIDANCE FROM THE CFSV2, AS WELL
AS WPC OUTLOOKS FOR WEEK 1 AND THE CPC WEEK-2 TEMPERATURE OUTLOOK.
PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE FURTHER ENHANCED FROM THE
SOUTHERN PLAINS INTO THE SOUTHEAST, SUPPORTED BY THE CFSV2 TEMPERATURE
FORECASTS, WPC OUTLOOKS FOR WEEK 1, AND CPC OUTLOOKS FOR WEEK 2 AND WEEK 3-4.
AVERAGE BELOW NORMAL TEMPERATURES ARE SLIGHTLY FAVORED FOR PARTS OF THE
NORTHEAST FOR THE MONTH OF AUGUST, WITH PREDICTED LIKELY BELOW NORMAL
TEMPERATURES FOR MOST OF THE FIRST HALF OF THE MONTH, WHEN CONFIDENCE IS HIGH,
FOLLOWED BY A SLIGHTLY ENHANCED PROBABILITY OF ABOVE NORMAL TEMPERATURES FOR
MOST OF THE NORTHEAST IN THE WEEK 3-4 OUTLOOK.
THE UPDATED AUGUST PRECIPITATION OUTLOOK FAVORS BELOW NORMAL PRECIPITATION FOR
SOUTHWESTERN AREAS OF THE ALASKA MAINLAND EASTWARD ALONG THE COAST INTO
SOUTHEAST ALASKA, SUPPORTED BY PRECIPITATION GUIDANCE FOR THE MONTH FROM THE
CFSV2. ABOVE NORMAL PRECIPITATION IS FAVORED IN A SWATH FROM THE NORTHERN
ROCKIES ACROSS PARTS OF THE HIGH PLAINS, THE CENTRAL PLAINS, AND OHIO VALLEY,
SUPPORTED BY THE LATEST CFSV2 MODEL FORECASTS, AS WELL AS CPC OUTLOOKS FOR THE
6-10 DAY AND WEEK-2 PERIODS. ABOVE NORMAL PRECIPITATION IS LIKELY FOR AUGUST,
PROBABILITIES EXCEEDING 50 PERCENT, FOR A SMALL AREA OF THE NORTHERN HIGH
PLAINS, WHERE WPC OUTLOOKS FOR WEEK 1 INDICATE CLIMATOLOGICALLY HIGH
PRECIPITATION AMOUNTS. ABOVE NORMAL PRECIPITATION IS FAVORED FOR THE EAST COAST
FROM PARTS OF THE CAROLINAS TO NEW ENGLAND, WITH MUCH ABOVE AVERAGE SEA SURFACE
TEMPERATURES OFFSHORE AND THE INFLUX OF MOISTURE. BELOW NORMAL PRECIPITATION IS
FAVORED FROM PARTS OF THE SOUTHWEST, THE RIO GRANDE VALLEY, AND THE GULF COAST,
TO THE FLORIDA PANHANDLE, SUPPORTED PRIMARILY BY CFSV2 MODEL FORECASTS FOR THE
MONTH.
---- PREVIOUS DISCUSSION FROM THE MID-JULY RELEASE FOLLOWS -----
THE MONTHLY TEMPERATURE AND PRECIPITATION OUTLOOKS ARE MADE UNDER STRENGTHENING
EL NIñO CLIMATE CONDITIONS. THE RECENT WEEK NIñO 3.4 SEA SURFACE TEMPERATURE
(SST) ANOMALY IS GREATER THAN +1.2 DEGREES CELSIUS. SSTS ACROSS THE CENTRAL AND
EASTERN EQUATORIAL PACIFIC OCEAN HAVE INCREASED SIGNIFICANTLY OVER THE LAST
MONTH. LOWER LEVEL WINDS AT 850 HPA ARE NEAR AVERAGE ACROSS MUCH OF THE
EQUATORIAL PACIFIC OCEAN, EXCEPT FOR WEAK EASTERLY ANOMALIES OVER PARTS OF THE
EAST-CENTRAL PACIFIC OCEAN. NEGATIVE OUTGOING LONGWAVE RADIATION (OLR)
ANOMALIES ARE PRESENT JUST WEST OF THE DATE LINE, INDICATING ANOMALOUSLY
ENHANCED CONVECTION. THESE OCEAN AND ATMOSPHERE CONDITIONS INDICATE THAT THE
ONGOING EL NIñO IS STRENGTHENING. WHILE IT IS EXPECTED THAT TELECONNECTIONS
BETWEEN THE TROPICS AND THE CLIMATE OVER NORTH AMERICA WILL TAKE TIME TO BE
ESTABLISHED, EL NIñO MAY IMPACT TEMPERATURE AND PRECIPITATION PATTERNS IN THE
NEAR FUTURE AND PLAYS A ROLE IN THE AUGUST TEMPERATURE AND PRECIPITATION
OUTLOOKS. THE MADDEN JULIAN OSCILLATION (MJO) WAS DISORGANIZED DURING THE LAST
MONTH, THOUGH DYNAMICAL MODELS INDICATE THAT THE MJO MAY BECOME ACTIVE OVER THE
MARITIME CONTINENT AND PROPAGATE ACROSS THE WESTERN PACIFIC IN THE NEXT FEW
WEEKS. HOWEVER, THE MJO FORECAST APPEARS SOMEWHAT UNCERTAIN AT THIS TIME AND
WAS NOT USED AS A SIGNIFICANT FACTOR IN THE AUGUST MONTHLY OUTLOOK.
THE AUGUST TEMPERATURE AND PRECIPITATION OUTLOOKS WERE PRIMARILY BASED ON A
SKILL-WEIGHTED CONSOLIDATION OF STATISTICAL AND DYNAMICAL FORECAST TOOLS. THE
FULL CONSOLIDATION INCLUDES A CONSOLIDATION OF RECENT DYNAMICAL MODEL FORECASTS
FROM THE NORTH AMERICA MULTIMODEL ENSEMBLE (NMME) FOR THE MONTH OF AUGUST. IN
ADDITION, THE FULL CONSOLIDATION INCLUDES A CONSOLIDATION OF THE CANONICAL
CORRELATION ANALYSIS (CCA), THE CONSTRUCTED ANALOG (CA), AND AN ENSO OCN TOOL,
THAT COMBINES THE IMPACT OF ENSO, BASED ON THE FORECASTS OF NIñO 3.4 SST
ANOMALY, WITH THE OPTIMUM CLIMATE NORMAL (OCN) REPRESENTATION OF DECADAL
TRENDS. DAILY INITIALIZED FORECASTS FROM THE NCEP CFSV2 DYNAMICAL MODEL, THE
MOST RECENT CPC WEEK 3-4 OUTLOOK THAT OVERLAPS THE BEGINNING OF THE MONTH OF
AUGUST, AND A STATISTICAL MULTIVARIATE LINEAR REGRESSION (MLR) FORECAST FOR THE
FIRST HALF OF AUGUST USING THE CURRENT NIñO 3.4 AND MJO INDICES AS PREDICTORS,
WERE ALSO CONSIDERED. RECENT BOUNDARY CONDITIONS, INCLUDING NEAR COASTAL SSTS
AND SOIL MOISTURE ANOMALIES, WERE ADDITIONAL FACTORS CONSIDERED.
THE AUGUST TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES OVER MUCH OF
ALASKA, CONSISTENT WITH DYNAMICAL MODEL GUIDANCE AND THE MONTHLY TEMPERATURE
CONSOLIDATION. FORECASTS OF EQUAL CHANCES (EC) OF ABOVE, NEAR AND BELOW NORMAL
TEMPERATURES ARE INDICATED FOR THE WEST COAST OF ALASKA, WHERE BELOW AVERAGE
SSTS SHOULD MODERATE AIR TEMPERATURES. EQUAL CHANCES (EC) IS ALSO FORECAST FOR
THE NORTHEAST MAINLAND, WHERE TOOLS ARE INCONSISTENT. WIDESPREAD ABOVE NORMAL
TEMPERATURES ARE FAVORED OVER MUCH OF THE CONTIGUOUS U.S. (CONUS), SUPPORTED BY
THE CONSOLIDATION OF STATISTICAL AND DYNAMICAL FORECAST TOOLS. PROBABILITIES
FOR ABOVE NORMAL TEMPERATURES EXCEED 60 PERCENT OVER THE PACIFIC NORTHWEST, DUE
TO DYNAMICAL MODEL FORECASTS AND DRY SOIL MOISTURE ANOMALIES. BELOW NORMAL
TEMPERATURES ARE FAVORED FOR PARTS OF THE EASTERN NORTHERN PLAINS AND UPPER
MISSISSIPPI VALLEY. EL NIñO IMPACTS FAVOR POTENTIAL TROUGHING OVER THE EASTERN
CENTRAL CONUS WITH NORTHERLY FLOW INTO THIS REGION. STATISTICAL FORECASTS BASED
ON THE CURRENT STATE OF ENSO PREDICT A LARGER AREA OF FAVORED BELOW NORMAL
TEMPERATURES, RESULTING IN A REDUCTION IN PROBABILITIES OF ABOVE NORMAL
TEMPERATURES FOR MUCH OF THE EAST-CENTRAL CONUS. ABOVE AVERAGE SST ANOMALIES
ALONG THE GULF AND EAST COASTS INCREASE THE PROBABILITY OF ABOVE NORMAL
TEMPERATURES IN THESE REGIONS.
THE AUGUST PRECIPITATION OUTLOOK FAVORS BELOW NORMAL PRECIPITATION NEAR THE
COAST OF THE SOUTHWESTERN ALASKA MAINLAND, SUPPORTED PRIMARILY BY DYNAMICAL
MODEL FORECASTS FROM THE NMME AND THE CONSOLIDATION OF PRECIPITATION FORECAST
TOOLS. THOUGH ABOVE NORMAL PRECIPITATION IS SLIGHTLY FAVORED IN SOUTHWESTERN
ARIZONA AT THE START OF THE MONTH BY THE WEEK 3-4 OUTLOOK, EL NIñO IMPACTS AND
STATISTICAL FORECAST TOOLS FAVOR A SUPPRESSED MONSOON FOR THE FULL MONTH OF
AUGUST. BELOW NORMAL PRECIPITATION IS FAVORED FOR MUCH OF THE SOUTHWEST MONSOON
REGION FROM WEST TEXAS TO NORTHEASTERN ARIZONA AND NORTHWARD ACROSS THE
INTERMOUNTAIN WEST INTO PARTS OF EASTERN OREGON AND SOUTHERN IDAHO. ABOVE
NORMAL PRECIPITATION IS FAVORED FROM EASTERN AREAS OF THE CENTRAL PLAINS ACROSS
THE CENTRAL MISSISSIPPI VALLEY TO THE ATLANTIC COAST, ALONG A PREFERRED
POTENTIAL STORM TRACK AND SUPPORTED BY THE CONSOLIDATION OF PRECIPITATION
FORECAST TOOLS. ABOVE NORMAL PRECIPITATION IS FAVORED FROM NORTHEASTERN FLORIDA
ALONG THE ATLANTIC COAST INTO SOUTHERN NEW ENGLAND, SUPPORTED BY THE
CONSOLIDATION.
FORECASTER: DAN COLLINS
THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1991 AND 2020, FOLLOWING
THE WORLD METEOROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3
COMPLETE DECADES AS THE CLIMATE REFERENCE PERIOD. THE PROBABILITY ANOMALIES
FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT
SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS.
THE NEXT MONTHLY OUTLOOK...FOR SEP ... WILL BE ISSUED ON THU AUG 17 2023
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
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